Nanotechnology Research in Materials Science and Engineering
The Department of Materials Science and Engineering at the University of Maryland is deeply invested in nanotechnology research and initiatives, facilities, and education throughout campus and with collaborators at national research laboratories.
Nanotechnology and Nanoscience Research and Initiatives
MSE faculty, graduate students, and even some undergraduates are engaged in a variety of high-profile nanotechnology-based projects whose discoveries could lead to advances in computer and electronic device manufacturing, biological threat detection, microscopy, and the treatment of disease. Below are only a few examples:
Ferromagnetic and Ferroelectric Nano-Materials
Manfred Wuttig, Professor
Above: Top view of ferromagnetic nano-cylinders (100nm high) embedded in a ferroelectric matrix. Picture taken with an atomic force microscope. Below: Top view of concentric super paramagnetic (dark blue) and paraelectric (green) nano-rings. Picture taken with a transmission electron microscope.
Professor Manfred Wuttig and alumnus Shenqiang Ren are working on the synthesis of ferromagnetic and ferroelectric nano-materials. If properly mixed with polymers and spun into films, these materials configure themselves automatically into distinct patterns that are potentially useful. The pictures display two patterns that evolve by mixing their components at different ratios. Each has distinct magnetic properties: The system of superparamagnetic nano-cylinders embedded in a paraelectric matrix (left, top image) could improve the capacity and reception of telecommunication circuits, and help create "virtual antennas". The ferromagnetic "nano-onion" (left, bottom image) might help configure new forms of memory. The material can make certain electronic devices faster and easier to manufacture, as well as more reliable because they would require fewer parts. Wuttig and Ren's materials are both more finely tunable than those currently available, and more easily tuned. For more information, see S. Ren, R. M. Briber and M. Wuttig, "Diblock Copolymer Based Self-Assembled Nano-Magneto-Electric," Applied Physics Letters 93, 1 (2008).
The properties of nanoparticles strongly depend on size and shape. A silver ring on one's finger is not very different than a silver coin: They have the same color, they same conductivity, the same rate of oxidation. By contrast, a silver nanoring is different than a silver nanodisk, and both are different from a silver nanosphere and a silver nanocube! Graduate and undergraduate students in the department who participate in the nanomaterials courses and laboratory research programs with Professor Oded Rabin are discovering methods to control the shape of nanoparticles using materials science principles. They have prepared libraries of silver nanoparticles of all the shapes mentioned above in the form of piles of small vials containing brightly colored solutions.
To make useful devices out of the particles, assembly is a key step in the process, and a very challenging one given that the particles cannot by seen or picked individually. Rabin and his students are devising methods for assembly based on a lock-and-key approach: They pattern cavities in a substrate (using electron beam lithography) and "encourage" the particles to self-assemble in those cavities. If the size and shape are correct, the nanoparticles will follow the assembly "instructions" and rest in the desired locations. In the SEM image above, the group's nanocubes took positions in the array of pores only 100nm in diameter.
Their method to drive silver nanocubes to self-assemble into clusters in predetermined locations is key to making sensors that take advantage of the unique properties of the nanoparticles. Prof. Rabin‚Äôs group prepared chemical sensors containing dimers, pairs of nanocubes, that are more effective than sensors with individual or randomly-placed nanocubes. The group is investigating the effect of particle shape and particle-particle interactions on the efficiency of their sensors.
For more information, see "Nanocube Pairs Are Key to Improved Sensors"
Nanoparticle Enhanced Fluorescence
R. J. Phaneuf, Professor
Calculated electric field intensity (E2) distribution at the distance 80 nm from the surface of a silver nanoparticle and a silicon substrate. The particle diameters are 60, 100, 120, and 210 nm for panels (a), (b), (c), and (d), respectively. As shown in panel (a), the incident light propagates downward and the polarization of the E-field is parallel to the substrate (colored in green). The wavelength of the incident light is 388 nm wavelength (514 nm in air). The color table indicates the field intensity normalized to the incident light intensity. Panels (e), (f), (g) and (h) are cross sectional renderings of electric field intensity (E2) for particle diameters of 60, 100, 120, and 210nm, respectively; panels (j), (k), (m) and (n) are cross sectional renderings of the electric field intensity (E2) for the same particle diameters, but for a SiO2 substrate.
Strong resonant coupling between light and plasmons in silver or gold nanoparticles leads to a number of striking and technologically important optical effects, among them the enhancement of fluorescence from nearby molecules. Since fluorescence is the technique of choice for many biological assays, significant enhancement would greatly enhance the sensitivity of these assays to a host of target biomolecules. To date, the maximum enhancement available in fluorescence has not been established. This is largely due both to difficulties in controlling the size and shape of the particles, and to the multiplicity of contributing factors: increased radiative decay rate and enhanced electric fields at resonance, "hot spots", i.e. regions of high field between closely spaced particles. The substrate is known to play a role as well; in particular there have been suggestions that certain substrates might play an active role in light-plasmon coupling rather than merely shifting the resonance frequency. In recent work the Phaneuf Group, including graduate student Shu-Ju (Phoebe) Tsai, observed just such an effect, in which the size dependence of the enhancement of fluorescence from monodisperse silver nanoparticles is profoundly altered by the Si substrate. Comparing fluorescence measurements with calculations of the response of the silver nanoparticles to incident light, they found that unlike what is commonly assumed, the variation of the fluorescence enhancement with nanoparticle diameter does not simply follow that of plasmon excitation as measured by the optical extinction. Instead it is the generation of regions of high electrical field intensity near the particle which dominates the fluorescence enhancement that are observed, and that a silicon substrate plays an active role in this regard: sweeping these regions out from beneath the particles as their size approaches the optimum for fluorescence.
For more information, please see the MSE research spotlight "Nanoparticle-Enhanced Fluorescence."
Nanotechnology Facilities and Laboratories
Our students, faculty and staff have access to and manage world-class facilities such as the Maryland NanoCenter, which includes the FabLab, a 10,000 ft2 clean room that supports research and development programs in micro-electromechanical systems, semiconductors, materials and devices for electronics, bioscience and bioengineering, and sensor/actuator systems; and the NISPLab, a microscopy facility focused on the characterization of materials and structures in the areas of biomaterials, multifunctional and smart materials, nanostructured materials, nanodevices and geological materials. The Keck Laboratory for Combinatorial Nanosynthesis and Multiscale Characterization conducts research using combinatorial materials science, scanning nanoprobes, and highly controlled materials synthesis.
For a more comprehensive listing of the Department's facilities and equipment, please visit our laboratories page.
The Department offers undergraduate- and graduate-level courses covering core concepts of nanotechnology and hands-on lab work. In 2007, members of the MSE faculty and their collaborators completed work on a National Science Foundation-funded project that developed new laboratory experiments that effectively engage undergraduate engineering students in the scientific processes and exploration of concepts in nanotechnology. Undergraduates experience the new curriculum in the Modern Engineering Materials Instructional Laboratory (MEMIL) and can gain additional research experience in our professors' labs.
The Department also administers the undergraduate Interdisciplinary Minor in Nanoscale Science and Technology.